The invention, generally, relates to the field of producing wood flakes. Further, the invention is related to the field of profiling logs, wherein, during the profiling, flakes are generated.
More specifically, the invention is related to an apparatus for producing an essentially wedge-shaped wood flake, wherein the flake is chipped out of the wood by means of a chipping tool rotating about a first axis such that it has a first, concave surface and a second, convex surface, delimiting between them the flake.
Further, the invention is specifically related to an apparatus for profiling a log, comprising a chipping tool rotating about a first axis for chipping out longitudinally extending corners from the log, and means for cutting off lateral boards from the log, one narrow side of which being configured by a lateral surface of the corner, and a circular saw blade for guiding a saw cut along the other lateral surface prior to chipping out the corners.
In the technology of wood processing it is generally known to partially or entirely chip wood by means of so-called chipping tools. Chipping tools are conventionally rotating tools having chipping knives along their periphery. Chipping tools are conventionally mounted stationarily and the wood to be partially or entirely chipped is guided along the chipping head in an axial direction of the wood.
Due to these circumstances, the wood flakes so generated have a wing-type shape with an essentially wedge-shaped cross-section. The wood flakes are delimited on their two large surfaces by a concave and a convex side, respectively, wherein these sides extend from a thick end of the wood flake towards a narrow end or, speaking in terms of a cross-sectional view, towards a tip in which the two surfaces converge tangentially.
Wood flakes are a valuable raw material for various industrial areas. Among these are the cellulose industry, the paper industry but also manufacturers of wood materials and so-called composite components, i.e. planks, boards and beams produced by gluing together wood flakes.
These wood flake processing industries accept wood flakes according to a specific classification. Wood flakes of medium size are highly preferred because when the wood flakes are too large, they are difficult to process and, if the wood flakes are too small or too thin, then during the production of cellulose, paper, wood materials or composite components losses occur or insufficiently stable structures are obtained.
The classification of wood flakes supplied is the decisive criterion for the price which the wood processing industry is prepared to pay for such wood flakes. Therefore, within the wood processing industry there is an important demand that, during the production of wood flakes as much as possible such wood flakes shall be produced which within the classification of the wood flake processing industry given will achieve the highest price.
If wood flakes are produced by means of a rotating chipping tool, as described above in more detail, they have a thinly terminating end along their wedge-shaped cross-section. This thin end is a disadvantage for the further processing of such wood flakes because the thin end will either entirely be dissoluted within the pulp or will result in less stable areas during the production of composite components.
In practice, wood flakes are produced by either entirely chipping wood into wood flakes or by chipping wood flakes out of the wood.
A partial chipping of wood, for example, takes place in the course of the so-called profiling of logs. This term is to be understood to mean an all-side processing of the initially raw log for giving it a predetermined cross-sectional shape (profile) so that the profiled log during subsequent sawing may easily be dissected into boards and beams. A corresponding method together with an appropriate apparatus is, for example, disclosed in DE 29 28 949 A.
According to these prior art methods and apparatuses, the logs are worked by means of so-called corner millers prior to the profiling which, in an axial direction, mill corners from the log so that the log, having been flattened before or being flattened thereafter, assumes a profile from which so-called side planks may be sawn away.
DE 37 02 980 C2 discloses a corresponding method together with an appropriate apparatus. According to the prior art method a first, for example horizontal saw cut of a predetermined depth is applied first from one side of the log, wherein in that case the axis of rotation of the saw blade extends vertically. After the application of the saw cut or (when a combined tool head is utilized) simultaneously thereto a partial area of the wood above the saw cut is chipped away, wherein the rotational axis of a chipping tool or, respectively, in a combined tool head the common rotational axis, extends vertically. The area chipped away does not extend as far in a horizontal direction into the log as the first saw cut is deep. Thereafter, in a further working step the residual area above the horizontal saw cut is chipped away, namely by means of a chipping tool, the rotational axis of which extends horizontally in the given example. Thereafter or together with the chipping away process step a second, vertical saw cut is applied in which the bottom of the groove so generated lies with its center where the first, horizontal saw cut was terminated within the wood. As a result, an area is worked out of the log being similar to a corner, however, being stepped at the bottom of the corner. It is important to note at this instance that never one of the two chipping tools engages an area that had been sawn before. In this prior art method, so-called xe2x80x9ccomma chipsxe2x80x9d are exclusively generated likewise as was described above.
EP 0 770 461 A2 discloses a method and an apparatus for dissecting logs into small wood products. According to this method the log is profiled in that first the corners are entirely sawn away by means of circular saw blades having axes being oriented 90xc2x0 with respect to each other. During the sawing out wood strips are generated that have to be removed from the profiling installation and have to be chipped in a separate chipping machine.
EP 0 775 558 A1 discloses a method for working logs. According to this method a vertically extending band saw is first guided longitudinally through the log wherein, as an alternative, also circular saw blades are suggested. In any event, the saw cut is positioned in a vertical plane such that it separates a side plank from the log. A separator element follows the saw blade along the sawn gap so as to keep the side plank being still integrally connected to the log in a distance from the remaining wood piece. A combined edging tool follows the separator element rotating about a vertical axis and which, as already described above, consists of a chipper and a circular saw blade connected therewith. By means of this tool, the corner area above the narrow side of the side plank to be produced is chipped away and, concurrently, the narrow side of the side plank is worked by the circular saw blade in a high surface quality. Within the chipping tool the chipping knives and the circular saw blade have the same cutting radius. The cutting circle extends tangentially relative to the broad side of the side plank to be separated, in other words, the saw teeth and the chipping knives do not run into the groove generated by the band saw acting upstream. However, also if in this prior art method the cutting circle of the chipping knives were to extend into the groove, this would have no consequences within the scope of the present invention because band saws, as well known in the art, only generate extremely narrow kerfs which, typically, have a maximum width of 3 mm. Therefore, only the outermost tips of the flakes would be affected. This, however, would only result in an unimportant modification of the flake shape. Therefore, according to this prior art method, only the already mentioned xe2x80x9ccomma chipsxe2x80x9d are generated by principle.
According to all afore-mentioned prior art methods and apparatuses, therefore, conventional wood flakes having a thinly converging end on the one hand and saw dust on the other hand, are generated.
DE 43 37 682 C1 discloses a method and an apparatus for dissecting a log.
According to the prior art method, side planks are sawn away from a laterally flattened log by means of a circular saw, the side planks being still provided at their edges with barks. These side planks, as long as they are still integrally connected with the log at their upstream end, are bent away and, thereafter, run essentially parallel to the log at a distance thereto. Within this distant position the side planks are chipped at their narrow sides by means of an edging chipper and are, hence, edged. The cutting edges of the edging chipper extend under approximately 45xc2x0 angle of engagement in a radial direction through the wood when in the vicinity of the barks. The side planks, therefore, almost run in the area of the rotational axis of the edging chippers and past the latter. This is possible because, as mentioned above, the side planks at this moment are guided at a lateral distance from the main wood. The purpose of this measure is to generate so-called xe2x80x9cuniform thickness chipsxe2x80x9d during the edging of the side planks having been bent away before, i.e. chips which, in contrast to the so-called xe2x80x9ccomma chipsxe2x80x9d have an essentially constant thickness parallel to the wood fiber. These xe2x80x9cuniform-thickness-chipsxe2x80x9d have approximately the cross-sectional shape of a parallelepiped, the corner angle of which being about 45xc2x0 (and 135xc2x0, respectively) because the plane of engagement of the chipper on the wood lies, as mentioned above, under approximately 45xc2x0 relative to the direction of movement of the side plank.
This prior art method and the corresponding apparatus, therefore, have the advantage to generate chips being advantageously configured for a subsequent processing within the cellulose industry, however, this disadvantage may only be obtained with substantial additional efforts because the side planks have to be bent away from the sawing plane and have to be edged in a significant distance from the main wood. However, this is not possible in the same manner for all woods, at least not without damaging the fiber of the side plank during the bending away.
It is, therefore, an object underlying the invention to improve a wood flake as well as methods and apparatuses of the type specified at the outset and the above-mentioned uses, respectively, such that the afore-mentioned disadvantages are avoided. In particular, it shall become possible to produce wood flakes in an economically optimum manner and with a shape corresponding exactly to those classes of wood flakes for which the wood flake processing industry is ready to pay the highest prices.
According to the apparatus for producing a flake, specified at the outset, this object is achieved in that the first axis extends horizontally, and that a circular saw blade is provided rotating about a second, vertical axis which, prior to the chipping, removes the wood in the area in which the surfaces intersect in an imaginary tip.
According to the apparatus for profiling a log, specified at the outset, this object is, further, achieved in that the circular saw blade is adapted to be rotated about a vertical axis, and that the chipping tool extends with its cutting radius into the groove generated by the saw cut such that it runs freely therein.
More specifically, the object is achieved by an apparatus for producing an essentially wedge-shaped wood flake, comprising a chipping tool rotating about a first, horizontal axis for chipping the flake out of the wood such that the flake has a first, concave surface and a second, convex surface, the flake being delimited between the surfaces, and a circular saw blade rotating about a second, vertical axis for removing wood in an area in which the surfaces intersect in an imaginary tip, prior to the chipping out.
Further, the object is also achieved by an apparatus for profiling a log, comprising a chipping tool rotating about a first, horizontal axis for chipping longitudinally extending corners out of the log, the corners having a first and a second lateral surface, means for cutting off lateral boards from the log, one narrow side of which being configured by the first lateral surface, a circular saw blade rotating about a second, vertical axis for guiding a saw cut along the second lateral surface prior to chipping out the corners, thereby generating a groove, wherein the chipping tool has a cutting radius extending into the groove such that the chipping tool runs freely in the groove.
The object underlying the invention is thus entirely solved.
In contrast to conventional, wedge-shaped chips having a thinly extending terminal end or tip, respectively, the invention suggests to remove that thinly terminating end so that only the thicker end of the wood flake survives.
A shortened wood flake of that kind has much more economical value and, hence, may be processed much more advantageously. The operator of a saw mill may, hence, expect a significantly higher economical yield during the processing of wood flakes if wood flakes of that shape are used.
The fact that according to the inventive apparatuses the circular saw blade axis of rotation extends vertically and the chipping tool axis of rotation extends horizontally, has the advantage that smaller drive units may be used, such that several advantages are achieved, both under economical and under design aspects.
Unlike in the apparatus disclosed in EP 775 558 A1, the circular saw blade is not used for cutting off a sideboard, instead, it is used for generating a slot or groove of finite depth.
The circular saw blade, preferably, has a thickness of more than 5 to 6 mm. The circular saw blade is, still more preferably, followed by a wood cleaver extending between the circular saw blade and the chipping tool.
This measure opens up the possibility to prepare during one and the same operational step the wood to be entirely or partially chipped by a cut, in particular by a saw cut, such that for a subsequent engagement of the rotating chipping tool the afore-mentioned shortened wood flakes are generated, almost immediately because that area had been removed before in which the thinly converging ends or tips, respectively, would have been made.
Moreover, according to another aspect of the invention the flake has a center line extending between the surfaces and being subdivided into a first center line section lying inside the flake and a second center line section lying outside the flake and comprising the tip, the second center line section having a length of between 40% and 100% of a length of the first center line section.
Further advantages will become apparent from the drawing and the enclosed description.
It goes without saying that the features mentioned before and those that will be explained hereinafter may not only be used in the particularly given combination, but also in other combinations or alone without leaving the scope of the present invention.